Dishwasher detergents incorporate persalts such as perborates and percarbonates for spotless results. To activate these bleaching agents and in order to achieve an improved bleaching effect at wash cycle temperatures of 60° C. or below, dishwasher detergents generally further contain bleach activators or bleach catalysts, and it is particularly the bleach catalysts which have proven to be particularly effective.
Bleach catalysts based on various manganese-containing transition metal complexes are described in EP 0 458 397, EP 0 458 398 and EP 0 530 870 for example. The catalysts described in these applications are characterized in that they comprise at least one ligand from the group of triazacyclononanes. Binuclear oxygen-bridged complexes with manganese or iron as central atom and 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3-TACN) as ligand are particularly preferable.
The complexes referred to are highly active in that very low wash cycle concentrations are needed to ensure complete removal of tea stains from dishware. In most cases, a detergent tablet need only contain 2-8 mg of the complex for this. Bleach catalysts are therefore preferably used in dishwasher detergents in the form of ready-made granules. This is done not only to increase their storage stability but also to ensure homogeneous incorporation of minuscule catalyst quantities into the formulations, in particular in tablet applications.
Bleach catalyst granules and also methods of producing bleach catalyst granules are described in various patent applications. EP 509 787 for instance lays claim to a catalyst granule consisting of 2% manganese catalyst, 84% sodium sulfate and 4% sodium silicate. EP 0 544 440 describes abrasion-resistant granules containing the manganese catalyst, an inert salt from the group of chlorides or carbonates, and also mixtures thereof and a binder from the series of oxidation-stable polymers, alkali metal silicates or saturated fatty acids. DE 2007 039 651 envisages advantages for a granule composed of 0.1 to 30% of a bleach catalyst, 10 to 99% of a carrier material which carbonates and silicates, and also 0.1 to 5% of a binder from the group of organic polymers. The binder (polymer) is employed in the granulating step in the form of a solution or dispersion in water or an organic solvent.
WO 95/06710 and WO 95/06711 describe granules which, in addition to the catalyst, contain an inert material (zeolite or silicate) and binders from the groups of silicone oils, waxes, fatty acids/soaps or ethoxylated fatty alcohols or polyglycols, preferably with a melting point of 30 to 100° C.
WO 97/16521 lays claim to catalyst-containing particles comprising 40 to 99% of a carrier/binder having a melting point of 38 to 77° C., preferably selected from the group of polyethylene glycols, paraffin waxes or mixtures thereof.
WO 03/093405 describes co-granules consisting of a bleach catalyst, a bleach activator and, optionally, a coating. As shown in Example 1 of said application, a manganese(II) complex, a TAED powder and a tallow fatty alcohol ethoxylate (Genapol® T500, Clariant) are mixed in a Lödige mixer at 40 to 50° C. and then pressed by an extruder into noodle-shaped granules. WO 2010/115581 describes co-granules containing a) one or more bleach activators, b) one or more bleach catalysts and c) at least 5 wt % of one or more organic acids. Fatty acids, alcohol ethoxylates or polymers are referred to as possible binders. Judging by the examples, the preferred binder is Genapol® T500.
It transpires that granules based on fatty acids/soaps, silicone oils or waxes no longer meet the high requirements expected of a modern granular material for use in dishwasher detergents. At the comparatively low washing temperatures used today and in the short wash cycles, these granules no longer dissolve fast enough to fully release the catalyst, and thereby do not provide an adequate cleaning performance.
It further transpires that, surprisingly, granules containing [MnIV2(μ-O)3(Me-TACN)2](PF6)2.H2O or related compounds which have a triazacyclononane ring and contain one or more polyethylene glycols or fatty alcohol ethoxylates as carrier/binder will have a distinct amine odor after a certain storage period, and therefore are unsuitable for any commercial use in household products. It is believed that a certain proportion of the manganese complex decomposes during production and/or storage of the granules, releasing the ligand trimethyltriazacyclononane (TACN) or Me3-TACN, which has a pronounced amine-type odor. A similar observation is made on using aqueous solutions of polyacrylates as binders in the granulating step and then drying the granular material at elevated temperature. It is believed in this case that there are interactions of the acid function with the catalyst wherein some of the catalyst is decomposed or converted into an acid-overbridged variant of the original catalyst, and therefore no longer has the full efficacy.